1. Field of the Invention
The present invention relates generally to screws and more specifically to a self-tapping screw with an improved thread design which facilities automated application and painting of a washer.
2. Discussion of the Prior Art
Some self-tapping screws have a single cutting point that is disposed at a tip of a screw body. The single cutting point allows a user to drill through steel sheet. If a notch is formed in the tip of the screw body, part of the single cutting point will be lost. The notch improves the ability to drill through the steel sheet and deburrs the newly formed hole. An example of a single cutting point screw is found in U.S. Pat. No. 4,329,099 to Shimizu, et al. The cutting point is actually part of the thread which continues to the end of the screw body. The screw has a short second thread which does not continue to the tip. However, the Shimizu, et al. patent does not have a notch; a notch greatly improves the ability to drill through steel sheet. It is also easier to drill through steel with two flutes instead of one. Greater stability is obtained by using two flutes especially when drilling by hand.
Further, automated application of a washer to the self-tapping screw is hindered when there are two sets of threads having different major diameters. The automated application of the washer to the self-tapping screw with two different sets of threads, results in the washer being non-parallel to the shoulder of the self-tapping screw head. The washer must be parallel to facilitate painting thereof.
Accordingly, there is a clearly felt need in the art for a self-tapping screw with an improved thread design which facilitates the application of a washer to the self-tapping screw.